Why would anybody remain in California if they had the means to leave?
I have a number of close friends who live in California. Out of all of these, my wife and I one of only two couples who moved away. The rest remain.
Our friends, all of them, wish they could leave. But family ties overcome all for them. One of my close friends said: "watching my granddaughter play basketball is more important than moving away from this abomination of a State." Ironically, their son, his wife, and family moved to Bend, OR about 6 years ago. They had a stunningly beautiful home in Bend, up on a ridge with a view, but due to the local politics they felt it was a poor place to raise their children. They moved to Idaho. The family told me the breaking point was the Bend school district put a litter box in the restroom for a student who "identified as a cat." I can't prove or disprove that, but I don't think my friends would lie about it.
Also to some irony, the other couple who moved are extreme hard-left liberals. So they did not leave due to conflict about politics. They are both proud to be "up and down ballot voters" who vote 100% for a particular party regardless who is running.
This other couple who moved are our closest friends. They have combined government pensions of about $250,000/yr. They realized the 13% CA income tax bite of that was about $30,000+ per year. So he buys sailboats, motorcycles, and toys using that money instead. And travel. And, importantly, they had little family in the area. Ironically, they voted for every tax hike while CA residents, then left due to high taxation. Go figure.
So, the family roots grow deep. So lots of folks will stay in place. And, of course, there are millions who dream of migrating to CA which will help keep the population stable or maybe increase it. Just not very many coming in from other US States.